Chain Tensile Strength

By bacolmm, Posted January 20, 2003

Is the tensile strength of a chain a good indicator of how much it will resist stretching? Is it safe to assume that a chain with a higher tensile strength will stretch less than one with a lower tensile strength, or are there other factors involved?

By Bill, Posted January 20, 2003

Yes tensil strength is a measurement of something being pulled lineally or in simpler terms....stretched. Also other factors would be o-ring vs non o-ring. The o-ring chains keep the grim out from the rollers and reduces wear. I thought I'd try the did ERT, you know, the one the pros use, less rolling resistance and all that. That thing is a pile of dung I wore it out in a third the time of my stock o-ring. I guess if was a pro and had a FREE new chain to put on every race, I'd use them too. Since I'm not, I'll be going back to the o-ring type.

Bill

By techman, Posted January 21, 2003

It turns out that they usually also have the best surface treatments for resisting wear on the chains on which they use the best materials in terms of tensile strength, so you win two ways. I'm guessing you've read DID's (?) catalogue or whichever one was the first guys to emphasise tensile strength vs just saying "use this on a 125, use this on a 250" etc. The X-rings are more tolerant of flapping around etc in terms of staying sealed. Chain "stretch" usually comes in the form of bushing wear, not stretching the metal itself unless it is an incredibly crappy, cheap chain on a really big-motored, spin-out-abused bike. You can verify this by taking a worn out chain, lay it down straight and you can compress it back to it's original length side by side with a new chain, and then stretch all the slop out of it and see how much longer it is than the new chain. The length change comes from loose fit of the links to each other.

The other big wear point is the outer rollers. On a new chain they're tight on the bushings; on an old chain you can grab one between your fingernails and wiggle it side to side on the inner bushing. A severe amount of slop usually precedes cracking the roller right off the chain, leaving the bushing which doesn't then actually contact the sprocket. Instead, the two adjacent rolers take up the load and wear even faster, like an accelerating self destruct process. So, if you lose a roller on the trail, take it easy till you get home. These roller surfaces are also hardened against wear with varying degrees of quality.

Mid or higher $ chains are worth it because they prolong your sprocket life too, another chain wear-out related cost.